Granted, they're point estimates not time estimates, but it's the same idea -- what was our velocity this sprint, what were the tickets that seemed easier than expected, what were the ones that seemed harder, how can we learn from this to be more accurate going forwards, and/or how do we improve our processes?
Your tone suggests you think you've found some flaw. You don't seem to realize this is explicitly part of sprints.
I'm describing my experiences with variances based on many, many, many sprints.